Despite recent advances in cancer detection and treatment strategies, cancer continues to contribute significantly to human mortality and remains second only to heart disease as the leading cause of death in the United States. In 2008 there were an estimated 565,650 deaths from cancer and each year about 1,437,180 new cases of cancer are diagnosed. Among those, lung cancer, breast cancer, and cervical cancer are among the most significant. For example, lung cancer remains the leading cause of cancer death in men and women, resulting in more than 215,000 new cases a year and over 161,000 deaths each year. Similarly, breast cancer and cervical cancer continue to be significant causes of cancer death in women with estimates of over 40,000 and over 3,500 women dying each year from breast and cervical cancer, respectively.
Overall, the survival rate for cancer has risen in recent years, but designing effective treatment strategies for cancer patients still represents a major challenge. In this regard, it has become increasingly clear that the problem of cancer mortality cannot be solved by treatment alone, but must also be approached from a prophylactic standpoint. Intervention with compounds of natural origin, such as phytochemical agents, is considered one such effective means to not only treat cancer, but also to prophylactically address cancer development. However, many of the same problems that are encountered with the administration of traditional chemotherapeutic agents are also encountered with these compounds of natural origin.
Typically, chemotherapeutic agents are administered orally or intravenously in bolus doses to elicit a response. Oral delivery of the chemotherapeutic agents often presents a bioavailability problem, as a large part of the agents is destroyed in the gut and the remainder is, at least in part, detoxified during first pass in the liver. Systemic delivery overcomes this hurdle, but this route of administration often leads to undesirable dose spikes. Moreover, a major limitation of both oral and intravenous delivery of traditional chemotherapeutic agents is that high doses of the agents are usually required in order to achieve an effective tissue or plasma concentration, but the high doses generally result in undesirable toxicity.
Accordingly, there remains a need in the art for methods and compositions for the delivery of compounds of natural origin in controlled low doses over extended periods of time. In particular, there remains a need in the art for methods and compositions for delivering low doses of phytochemical agents in a sustained manner such that phytochemical agents can effectively be used to address cancer mortality from both a therapeutic and prophylactic standpoint.